Protecting-varnish for electrodes of electrolytic cells



' UNITED STATES,

PA ENT OFFICE.

. THOMAS A. Enrson, or LLEWELLYN PARK, new JERSEY.

PROTECTING-VARNISH FOR ELECTRODES OF ELECTROLYTIC CELLS.

No Drawing.

for Electrodes of Electrolytic Cells, of whichthe following is adescription.

My invention relates to varnishes for protecting members or articlesdisposed as electrodes in electrolytic cells, as, for example, where itis desired to protect surface portions of members disposed as cathodesin electroplating cells from any action or deposition of metal thereonin the operation of the cells, members. I

The invention resides in an improved varnish for this purpose which isvery effective and which is not aflected either by acid or alkalineelectrolytes, and also in an electrode for electrolytic cells providedwith a rotecting coating of such varnish.

y invention is based on the discovery that a varnish comprising acoumarone or para coumarone resin, when applied to a surface portion ofthe electrode of an electrolytic cell on which the plating takes place,usually the cathode, will more effectively protect such surface ortionfrom any action of the electrolyte and the deposition of any metalthereon, than any of the varnishes usually employed for this purpose. Inpreparing my improved varnish I dissolve a coumarone or para coumaroneresin in a suitable solvent, preferably toluol, until the solutionobtained is of such viscosity as to enable it to be readily applied tothe electrode which it is desired to protect by brushing or dipping.

here are a number of coumarone or para coumarone resins, the same beingobtained by subjecting the coal tar solvent naphthas to the polymerizingaction of strong sulfuric acid. The melting points of these coumarone orpara coumarone reslns vary considerably, and I prefer to employ for,

Specification of Letters Patent. Application filed September 29, 1919'.Serial No. 327,323.

so as" to rovide cut-outs on such I where two coats of the Patented Jan. 4, 1921.

my improved varnish that one of such resins having the highest meltingpoint, as I find that the best results are obtained thereby.

Two coats of the varnish prepared as described above are applied to thesurface portion of the cathode or electrode to be rotected, either bybr'ushing or dipping. pon drying, this varnish forms a very hard, oo-

herent and non-porous coating on the electrode which is attacked neitherby acid nor alkaline electrolytes. Moreover this varnish, unlikeother'varnishes heretofore employed for the same purpose, adherestenaciously to the surface portions of the electrode to which it isapplied, is not underrun by the electrolyte or plating bath of the cellin which the electrode may be disposed, and varnish are applied asdescribed, there are no fine holes or pores present in the surface ofthe coating of varnish and consequently the plating or deposition ofmetal at any point on the surface of the electrode beneath the varnishis prevented as the electrolyte cannot penetrate the varnish.

While I have described the preferred form of my improved varnish and thepreferred methods of preparing and applying the same, it is to beunderstood that my invention is to be limited only as defined by theterms of the appended claims.

Having now described my invention, what I claim as new and desire toprotect by Letters Patent, is as follows:

1. An electrode for an electrolytic cell having a surface portionthereof coated with a varnish -comprisinga coumarone or para coumaroneresin, substantially as described.

2. An electrode for an electrolytic cell having a surface portionthereof coated with a varnish, comprising that one of the coumarone orpara coumarone resins having the highest melting point, substantially asdescribed.

This specification signed this 24th day of September, 1919.

THOS. A. EDISON

